1. Field of the Invention
The present invention relates to a device for exchange of gas volumes, suitable for use in an anesthetic system.
2. Description of the Prior Art
In many anesthetic systems a portion of breathing gas circulates so that it is returned to a patient. This may range from the entire breathing gas to a component in the breathing gas (anesthetic agent). The gas that is exhaled contains carbon dioxide. This is diluted in certain systems and it is filtered out in others.
Both of the variants result in certain disadvantages. In the former case there is often a large waste of fresh gas (including costly gases) and in the other case a flow resistance is introduced in the system.
In one type of anesthetic system a unit for adsorption and desorption of gaseous anesthetic is used. This results in anesthetic gas being selectively returned to the patient whilst other components in the breathing gas are replaced with every breath.
However, the unit unavoidably occupies a certain physical volume, which has the consequence that a certain amount of carbon dioxide may be stored in the unit and re-supplied to the patient with the consecutive breath. The amount of carbon dioxide does not constitute a risk to the patient but may disturb the acquisition of carbon dioxide level measurement curves (capnogram).
This amount may be easily trapped using a small absorber unit for carbon dioxide but, as mentioned above, the flow resistance may increase with every unit in the system.
A desire therefore exists to find a solution that minimizes the level of carbon dioxide without the need to use a resistance-increasing component.